In well known sheet separating devices, as exemplified in German Pat. DT-AS 1 611 372, the upstream roller as well as the downstream roller, relative to the sheet conveying direction, both have a concentric configuration and continuously contact the sheet directly beneath them. A jam inhibitor is generally associated with the downstream separator roller. The jam inhibitor is made of a soft rubber material and fixed to the supply hopper. It enables sheets having different thickness and characteristics to be processed without the risk that two or more sheets being simultaneously engaged and propelled.
Experience has shown, however, that engaging and separating of the uppermost sheet of a stack of sheets is not performed with desired regularity, as for example, the feeding of envelopes or documents to a printing station wherein an imprint has to be made upon a precise predetermined area. Factors which can effect the regularity are, for instance, the differing quantity of the sheets in the stack of sheets, their differing "fanning out" properties, their varying angle to the horizontal, and, not least, the dissimilar adhesion values and stiffnesses. The object of this invention is to provide an improved sheet separating device of the type described before which avoids the above disadvantages and which attains a simple performance that guarantees an accurate separation of the sheets to be fed independent of their properties, sizes and characteristics.